Agreed: your back will thank you for getting a lighter boat.

I own a 2006 VectorWorks Blade F-16. You could certainly pick one of these up within your price range. These are solid boats. But be aware that the older F-16s like this are very demanding downwind. The newer designs like the Falcon and Viper might be easier to keep upright, but probably not within the budget.

If you mostly sail solo and want something light and cheap and within the budget, consider an old A-cat like a 2000ish Boyer Mk 4. Your back will love you. And you won't miss the spinnaker.

-Geoff